Transportation of materials from one location to another requires energy and is usually achieved either by a transporting vehicle or, when the material to be transported is fluid or particulate, by flow. In the first case the movement is done by a device equipped with a motor or other mechanical arrangement that performs work involving such movement. In the second case the movement results directly from forces due to pressure differences, gravitation, etc.
In all such cases the required energy is obtained from various sources such as burning fuel, electric current, etc. In practice, gravitation and similar forces cannot maintain movement continuously and effectively.
A source of energy that has only recently been used to directly create movement, although predicted by Maxwell's theorem, is light. It is now well established that a light beam illuminating a solid surface, preferably of reflective nature, exerts force or pressure on that surface. Such forces are also well known in astronomy. Light force or pressure, has recently been utilized, for example using laser beams, to maneuver micro-organelles and even molecules within cells and often termed optic tweezers.